What is the best way to word this sentence in Chinese.
I am trying to say "he is a teenager today" in Chinese. I thought I would know how to say this but when I googled the different ways I thought I could say it, I found no sentences like it.
The full sentence I want to write is: It's my eldest son's birthday today, he's a teenager today! I know I can say 他今天十三岁了, but I really want to use the word "teenager".
Thank you for your help in advance.